#include <iostream>
#include <cmath>

/**
 * Computes the Euclidean distance between two points (x1, y1) and (x2, y2).
 *
 * @param x1 a double
 * @param y1 a double
 * @param x2 a double
 * @param y2 a double
 * @return the Euclidean distance between (x1, y1) and (x2, y2)
 */
double euclidean_distance(double, double, double, double);

/**
 * Reads points in plane from standard input in form
 *
 * 0 0
 * 1 1
 * 3 1
 * 4 0
 *
 * and outputs the total length of the segments that
 * connect them.
 *
 * Compile with
 *
 * g++ -Wall -pedantic -std=c++17 -o Distance distance.cpp
 *
 * and then run with
 *
 * ./Distance
 */
int main(int argc, char **argv)
{
  double last_x, last_y;
  double x, y;
  double total_distance = 0.0;

  std::cin >> last_x >> last_y; // extract from stream cin (standard input)
  while (std::cin >> x >> y)
    {
      total_distance += euclidean_distance(last_x, last_y, x, y);
      last_x = x;
      last_y = y;
    }
  std::cout << total_distance << std::endl;
}

double euclidean_distance(double x1, double y1, double x2, double y2)
{
  double d = std::sqrt(std::pow(x1 - x2, 2) + std::pow(y1 - y2, 2));
  return d;
}